1. Field of the Invention
This invention relates generally to computer systems, and more particularly to methods and associated systems for transferring data between storage systems.
2. Description of the Background Art
For back-up purposes, data stored in a disk unit of a local mainframe computer system are copied to a remote storage device to prevent data loss in the event of a disaster such as a disk crash or facility shutdown. U.S. Pat. No. 6,098,129 to Fukuzawa et al. (xe2x80x9cFukuzawaxe2x80x9d) discloses a configuration for backing-up data from a mainframe computer system (xe2x80x9cmainframexe2x80x9d) to an open computer system. Although Fukuzawa discloses the use of low-cost open computer system storage devices for backing-up mainframe data, Fukuzawa does not disclose the use of another mainframe storage device for back-up.
Because mainframes are generally more reliable than other types of computer systems, data stored in the disk unit of a mainframe are ideally backed-up to a disk unit of another mainframe. Remote dual copy functions, which involve the backing-up of stored data from one computer system to another in real-time, have been performed between mainframes using the so-called Count-Key-Data (xe2x80x9cCKDxe2x80x9d) protocol. The CKD protocol allows currently available mainframes to transfer data at a rate of approximately 17 MB/s (mega-bytes/second). To increase the amount of data that can be copied from one mainframe to another within a period of time, it is desirable to obtain a data transfer rate that is faster than what is currently obtainable using the CKD protocol.
The present invention relates to a method and associated systems for transferring data between mainframe storage devices. While the invention is suitable for remote dual copy functions, the invention may be generally used in applications requiring data transfers.
In one embodiment of the invention, a local disk system of a local mainframe includes one or more local disk units. For back-up purposes, data in at least one of the local disk units are copied to a designated remote disk unit of a remote disk system. Data transfer between the disk units of the local and remote disk systems occurs over a fixed block infrastructure to increase data transfer rates. Accordingly, variable-length data received in the local disk system and destined to be backed-up to the remote disk system are first converted to fixed-length data prior to transmission over the fixed block infrastructure. In the remote disk system, fixed-length data received over the fixed block infrastructure are converted back to variable-length data.
In one embodiment of the invention, a method for performing data transfer between a local disk system and a remote disk system includes the steps of receiving variable-length data in the local disk system, converting the variable-length data to fixed-length data, sending the fixed-length data to the remote disk system, and converting the fixed-length data back to variable-length data in the remote disk system. The use of fixed-length data in the just mentioned method increases the data transfer rate between the local and the remote disk systems.
These and other features and advantages of the present invention will be readily apparent to persons of ordinary skill in the art upon reading the entirety of this disclosure, which includes the accompanying drawings and claims.